Food heating device

ABSTRACT

This disclosure describes a food heating device for heating and cooking food items such as TV-dinners which are prepackaged in standard electrically conductive containers. The device includes a rigid enclosure having a base and a cover for providing access to the interior of the enclosure to allow insertion or removal of the food package. The food package is supported on the base and, a step-down transformer supplies low voltage electrical power to the conductive food package. First and second clamps are supported by the enclosure means and clampingly engage first and second edge portions of the conductive food package, respectively, so that the electrical current passes directly through the food package and at least some of the food contained therein to rapidly and effectively heat the food.

a United States Patent [151 3,669,003 King [451 June 13, 1972 [54] FOODHEATING DEVICE 2,844,695 7/1958 McLean ..99/3$8 x [72] Inventor: LeonardTony King, 4109 Cedar Avenue, 3210199 10/1965 schlaf'm' Long Beach,Calif. 90807 3,257,934 6/ 7 3,385,952 5/1968 Mix ..99/171 X [22] Filed:June 22, 1970 Primary Examiner-Billy J. Wilhite [21] AppL'No" 48,209Attorney-Limbach, Limbach & Sutton Related US. Application Data [63]Continuation-in-part of Ser. No. 629,315, April 7, [57] ABSTRACT 1967,abandoned. This disclosure describes a food heating device for heatingand cooking food items such as TV-dinners which are [52] U.S.Cl.99/33l,99/ 171, 99/339, pre ackaged in standard electrically conductivecontainers. 219/383 The device includes a rigid enclosure having a baseand a [5 l] Int. Cl. 27/62 over for providing agcess to the interior ofthe enclosure to [58] Field ofSearch ..99/358, 171,221, 233,253, allowinsertion or removal f h f d k The f d 99/274 331; 219/383 package issupported 'on the base and, a step-down trans- I former supplies lowvoltage electrical power to the conductive [56] Referems C'ted foodpackage. First and second clamps are supported by the UNITED STATESPATENTS enclosure means and clampingly engage first and second edgeportions of the conductive food package, respectively, so that 2,532,0141 H1950 Davis X the electrical current passes directly through the foodpackage 2,013,675 9/ l 935 UP "99/182 and at least some of the foodcontained therein to rapidly and 3,573,430 4/1971 Eisler ....99/l71 X ffti l heat the food, 2,182,383 12/1939 Lang et al ....99/358 X 2,474,3906/1949 Aff...- ..L ..99/358 X 11 Claims, 8 Drawing Figures PATENTEDJUH13 m2 3. 668.003

SHEET 10F 3 FlG 1 M/l/iA/TOA: F I G 2 Leonard 7513 K/ng ,0 TTa/ENEYSPATENTEDJUR 13 I972 3,589,003

SHEET 2 0F 3 ll j W IN V ENTOR. Lzonqr'd 75w FOOD HEATING DEVICE Thisapplication is a continuation-in-part of copending application Ser. No.629,315 filed Apr. 7, 1967 now abandoned.

BACKGROUND or THE INVENTION Various prepackaged food items of whichTV-dinners are exemplary are now sold in containers constructed entirelyof a conductive material such as aluminum foil. It is common practice toheat or cook TV-dinners in a conventional oven. As is well known, inconventional ovens gas or electric heating elements heat the walls ofthe oven and the air within. The heated air in turn heats the food item.This is a slow and inefiicient operation and may consume up to 45minutes of time.

On the other hand, microwave ovens will thoroughly and rapidly heat fooditems. However, these ovens are very expensive and not feasible on adomestic scale. Moreover, they cannot be used to heat foods held inmetallic containers.

Several. prior art devices heat packaged food items by passingelectrical current directly through a specially constructed foodpackage. This has the advantage of more rapidly heating the food item.However, these prior art heaters require a specially constructedcontainer for the food. Often these containers include several layers ofdifferent materials and this significantly increases the cost of thefood package. Furthermore, each of these special heaters aresubstantially restricted in their use to food packages which have beenspecially designed for use therewith.

Specific examples of prior art devices include U. S. Pat. No. 3,210,199to SD. Schlaf wherein a special container for the food is provided. AlsoU.S. Pat. Nos. 3,230,861 and 3,257,934 to A. L. Korr require the food tobe placed in a special container. U.S. Pat. No. 2,182,383 to O. W. Langet al, provides for heating food during a canning process by passingcurrent through a tin can.

SUMMARY OF THE INVENTION The present invention overcomes the above noteddisadvantages in providing an inexpensive and efiicient heating devicewhich rapidly heats prepackaged food items. The heating device of thepresent invention is particularly adapted for use with the standarddisposable prepackaged food packages such as TV-dinners and the like andrequires no specially designed container. With the present invention thefood is rapidly heated'in the standard conductive container in which itwas packaged and sold to the consumer.

The present invention accomplishes these advantageous results by passingelectrical current directly through the standard conductive containerwhich contains the food. The food is in contact with the conductivecontainer and depending upon the particular characteristics thereof,some current will also pass directly through the food. Thus,substantially all of the energy applied is dissipated as heat in thefood producing very rapid and efficient heating without need for aspecial container for the food.

To further assure rapid and even heating of the food, it is preferred topass current from one longitudinal edge to the opposed longitudinal edgeof the container. Preferably the current is applied along the fulllength of the opposed longitudinal edges of the container. Many of thesestandard containers have an aluminum foil conductive top layer or coverso that the current is passed through the package in parallel pathsdefined by the cover and the body of the container, respectively. Thisprovides heat all around the food item.

With the present invention, prepackaged food items such as a TV-dinnercan be fully prepared for eating in from about 90 seconds to 7 minutes.Alternating current at low voltage, for example,0.6volts is used. Thisprovides rapid heating of the food package while making the package safeagainst electrical shocks.

Another advantageous feature of the present invention is that theelectrical current is passed directly through at least some of the foodwithin the conductive container. As the temperature of the metalcontainer rises, the resistance thereof will increase; however, as thetemperature of the water within or around the food rises, the resistancethereof, decreases. Therefore, as the entire food package is heated, alarger proportion of the current is passed directly through the food tofurther increase the speed and efficiency of the heating device.

A further advantageous feature of the. invention is that resistance andleakage reactance losses are minimized.

The concepts noted above are applicable to food heating and preparationin various environments not only as vending machines but preferably insimple, inexpensive domestic appliances for heating prepackaged fooditems such as TV-dinners. Such an appliance in one embodiment includes arigid enclosure for enclosing the food package. The enclosure includes abase on which the conductive container is supported and a removablecover for providing access to the interior of the enclosure. Low voltagealternating current is provided by a step-down transformer which iselectrically connectable to standard line voltage. A pair of clamps aremounted on the en closure for gripping the opposed edge portions of theconductive container to pass the low voltage current therethrough. In analternative embodiment a hinged cover is provided on the base; the coverwhen closed hold a pair of hinged clamps against the opposed edgeportions of the container. In a further embodiment, a pair of hingedcovers also function to clamp the package edges when the cover isclosed.

In one preferred form of the domestic appliance, the transformer formsall or a portion of the base. Each of the clamps includes an elongatedrigid member or first jaw mounted on the base and extending upwardlytherefrom. These upright members are spaced an amount corresponding tothe distance between edge portions of the conductive container. Thespacing between edge portions may be variable, if desired, toaccommodate food packages of different sizes. The removable covercontains a second rigid member which forms the second jaw of the clamp.When the cover is in position to close the enclosure, the two rigidmembers automatically grip the opposed edge portions of the conductivecontainer. Thus, by merely placing the conductive container in theenclosure the container automatically engages th'e upright rigid memberwhich serves as the lower jaw of the clamp and as supporting means forthe container. The closing of the cover closes the enclosure andautomatically clamps the conductive container in position.

In an alternative preferred embodiment of the domestic appliance, arectangular parallepiped enclosure is provided with a cover portionhinged along one edge of the enclosure. The step-down transformer issupported centrally in the enclosure and a pair of conductive panelsinsulated from the enclosure, connected to the transformer secondary,extend outward from the transformer and upward parallel to opposed sidesof the enclosure. Support for food packages to be heated is supplied bythe upward panel portion. Panels serving as clamps and hinged adjacentto the conductive panels clamp the food package against the conductivepanels when the enclosure cover is closed.

In a further preferred embodiment, the hinged clamps also serve as anenclosure cover by a proper choice of dimensions thereby eliminating aseparate cover.

A thermostat is preferably mounted to engage or substantially engage theconductive container for automatically opening the circuit to thetransformer when the conductive container reaches a predeterminedtemperature. In addition, a resistive heating element may be providedabove the container,

if desired to provide additional heat to particular portions of thedevice.

The invention, both as to its organization and operation I ing applianceof FIG. 3.

heating appliance according to one-embodiment of the present invention.

.FIG. 2 is a front elevational view of the heating device taken alongsection line 2'2 of FIG. I. I

FIG. 3 is a perspective view of a heating appliance according to anotherembodiment of the instant invention.

FIG. 4 is a cross-sectional front elevational view of the heat- FIG. 5is a schematic circuit diagram of a heating appliance according to anembodiment of the invention.

FIG. 6 is a plan view of an unfolded secondary winding.

FIG. 7 is a planview of an alternative unfolded secondary winding.

FIG. 8 is a front elevational view of 'a heating appliance according toa further embodiment of the present invention.

DESCRIPTION- OF THE PREFERRED EMBODIMENTS Referring to the drawing,wherein the same reference numerals will be'ca rried throughout thevarious figures to refer to like or identical parts, reference numeral11 designates a heating device in the form of an inexpensive applianceconstructed in accordance with the teaching of this invention.

Generally, in the embodiment of FIGS. 1 and 2, the heating device 11includes a base 13 and a removable or openable cover 15 which coactswith the base 13 to form an enclosure for a food package 17. The foodpackage 17 is held within the enclosure by a pair of clamps 19 and 21.

"The base 13 is formed primarily by a transformer 23. The transformer 23has the usual primary and secondary windings and an enlarged core 25which forms a major portion of the base 13.- The transformer 23 is ofthe step-down type and is connectible to a standard 1 10 volt AC outletby a pair of leads :The base 13 also includes four feet 29 constructedof rubber or similar material for supportingthe heating device 11 on asuitable supporting surface 31. The feet 28 may be suitably attached tothe core 25 by bolts 33. Two elongated block members 35 and 37 aresuitably attached to the upper surface of the core and extendlongitudinally for almost the full length of the core 25 as shown inFIG. 2. A second pair of block members 39 and 41 (FIG. 2) are securedto' the core 25 by the bolts 33and extend transversely of the heatingdevice 11 along the periphery of the core. v i

The cover 15 includes atop wall 43 and a peripheral wall 45 dependingtherefrom and overlapping the '-block members mounted on the core 25.-The cover 15 should be completely removable from the base 13 or at leastpivotable to a position in which access'to the interior of the enclosureis provided. In

the embodiment illustrated the cover 15 is releasably secured to thebase 13 by a pair of conventional toggle latches 47 and 49. Each of thetoggle latches 47 and 49 includes an upper or fixed latching member 51rigidly afiixed to the peripheral wall 45, a lower or movable latchingmember 53, and a toggle lever secured to the adjacent block member foroperating the movable latching member 53. A handle 57 in the form of aknob is secured to the top wall 43 of the cover'15.

The clamps l9 and 21 are identical and each of these clamps includes anelongated upright rigid member 59 secured to or forming a part of thebase 13 and an upper elongated rigid member 61 suitably secured to thetop wall 43 but insulated therefrom by an insulator 6 3.

Each of the upright members 59 extends longitudinally for substantiallythe full longitudinal length of the food package 17. Each of the uprightmembers 59 is a conductor electrically connected to or forming a part ofthe' secondary of the transformer 23. Preferably, the upright members 59are secured to the adjacent block members 35 and 37 so that these blockmembers will provide support for the upright member.

As shown in FIG. 1, the food package 17 has opposed conductivelongitudinal edge portions 65 and 67; These edge portions rest on theupright members 59 as shown and thus, the upright members 59 formsupporting means for the food package 17. v

The upper members 61 preferably extend longitudinally for substantiallythefull longitudinal length of the edge portions 65 and 67 and includejaw portions 69 whichcooperate with the upper ends of the associatedupright members 59 to securely clamp the edge portions 65 and 67 whenthe cover 15 is mounted on the base 13 as shown in 1.

The clamps l9 and 21 are spaced apart a distance to accommodate aTV-dinner of a standard size. This spacing between the clamps 19 and 21can be varied if desired, to accommodate food packages of differentdimensions.

The electrical current is supplied to'the food package 17 through theclamps 19 and 21 and it is preferred to provide the clamps along thelongitudinal edges of the food package 17. However if desired, theclamps may extend along the transverse edge portions of the food package17. I 1

The food package 17 is of a standard type and includes a container 71 ofconductive material such as aluminum foil. The container 71 has thelongitudinal edge portions 65 and 67 and transverse edge portions 73 and75 (FIG. 2) all of which have substantiallength. The container71 mayhave a plurality of the usual compartmentsKnot shown) for. containingdifferent food items. The container 17 has an upper wall '77 ofconductive material such as aluminum'foil which completely closes theupper end of the container 71. The container 71 and the upper wall 77provide two parallel .paths for the flow of current between the clamps19 and 21 to provide heat completely around. the food contained withinthe food package l7. The clamps 19 .and 21 should engage generallyopposed substantially spaced portions of the food package 17 to assurethat the resistance provided by each of the parallel paths will not begrossly disproportionate to obtain reasonably even heating across thetop and the bottom of the food package. 7 I

A thermostat 79 is mounted on the base13 in a position in which it isengageable with the lower surface of the container 17. The thermostat 79is connected to a switch (not shown) and automatically opens such switchwhen the temperature of the container 71 reaches a predetermined valuesuch as the boiling point of water. Opening of this switch opens thecircuit to the transfomier. If desired, the thermostat 79 could also bearranged to close thatswitch if the temperature of the confor browningcertain food items contained therein. In the embodiment illustrated, theheating element 81 extends substantially the full transverse width ofthe food package 17 and less than half of the longitudinal length of thefood package. The heating element 81 may be provided with electricalcurrent through separate leads 83 or through the upper member 61 of theclamps 19 and 21 if the member 61 is made of conductive material. Aswitch (not shown) may be provided to open and close the circuit to theheating element 81 without effecting the current flow to and through thefood package 17.

To use the food heating device 11, the cover 15 is removed and the foodpackage 17 is placed on the base 13 with the gitudinal edge portions 65and 67 of the food package 17. In

this position, the clamps l9 and 21 engage the longitudinal edgeportions 65 and 67 along substantiallythe full width thereof and thecontainer 71 and the upper wall 77 thereof provide two parallel pathsfor the flow of currentbetween two clamps 19 and 21.

By operating an appropriate switch (not shown) the transformer 23supplies current to the clamps l9 and 21. The transformer 23 may, forexample, reduce llO volt AC line voltage toabout 0.6 volts.Current isthus supplied through the container 71 and the food therein to rapidlyand efficiently heat the food. As the temperature of the food increases,the water content thereof offers proportionately less resistance to theflow of current and accordingly, the amount of current flowing throughthe food items themselves is increased. When the food within the foodpackage 17 is thoroughly heated, the 4 thermostat 79 is operative toopen the circuit to the food package 17. The time required may be, forexample, about 6 minutes. 7

If it is desired to utilize the resistive heating element 81, the foilforming the upper wall 77 may be peeled back to expose the food itemsdirectly beneath the resistive heating element 81. The resistive heatingelement 81 is supplied with current simultaneously with the applicationof current directly to the food package 17 to allow the resistiveheating element to brown the exposed portions of the food itemtherebelow. The food heating device may be sufficiently large tosimultaneous heat several TV-dinners, if desired.

In FIGS.3 and 4 an alternative embodiment of the heating device 11 isshown having a base 13 with a cover 15 hinged along the top rear edge ofthe base portion. When cover 15 is closed, a rectangular parallepipedenclosure is formed. Cover 15 is secured in the closed position by alatching member 85. A latching member (not shown) is provided on cover15 to mate with member 85. A pair of rigid upright supports 87 along theinside transverse sidewalls of base 13 support a pair of clamping plates89. Plates 89 are attached by hinges 91 and are free to rotate downwarduntil engaged by the upward extending portions of curved panels 93. Thetop edges of panels 93 are spaced so as to support the transverse edgesof a standard conductive food package. Panels 93 are conductive and arean extended portion of the secondary of a transformer 23 locatedcentrally in the base 13. Transformer 23 has a C- shaped core 24, aprimary winding 85, and a secondary 96. The secondary may be a singleturn winding and may be integral with panel pieces 93. Thus for example,secondary 96 and panels 93 could be a single piece formed in an S-shapeas shown unfolded in FIG. 6. The central portion of piece 96 would bewrapped around transformer primary 24. A second alternative is shown inFIG. 7, wherein the combination secondary 96 and conductive panel 93 isa modified horseshoeshaped piece. The left hand'portion would be loopedaround and threaded through the right central operative in order toencircle transformer primary 24. By making the support a portion of thetransformer secondary, the'voltage drop is kept low and the .closeproximity of the food container to the transformer reduces leakagereactance loss. In effect the container too becomes a part of thesecondary.

Panels 93 are insulated from the base portion 13 by insulating material97. Clamping panels 89 are formed from electrically non-conductivematerial. A pair of stops 98 located-at the ends of clamps 89 farthestfrom the hinge points engage the cover 15 when the unit is closed. Thusa food container 17 is placed over conductive end supports 93, clamps 89are folded down over the container, and cover 15 is closed therebyforcing a tight low-resistance contact between the transverse edges ofconductive container 17 and the conduc' tive panels 93 of thetransformer secondary. A thermostat 79 is provided on a spring support94 so as to engage the food package 17 when it is in place.

FIG. 5 shows the electrical connection of the heating appliances. Oneside of primary 101 of step-down transformer 23 is connected to one pinof line plug 99. The other side of primary 101 is interrupted by asingle-pole, single throw on/off switch 97 and a thermostat 79. When thethermostat reaches a predetermined minimum temperature its associatedswitch opens thus removing the line voltage from primary winding 101.The secondary winding 103 is connected to the edges of a conductive foodcontainer 17 via conductors 93 and good electrical contact is maintainedby clamps 89.

In FIG. 8 a modification of the heating unit of FIGS. 3 and 4 isdepicted having generally the same base and internal structure includingconductive support panels 93 connected to the transformer secondary. Afood'package 17 is shown in place supported along its transverse edgesby panels 93. A pair of combination clamping members and top covers arehinged at hinges 91 fixed-to the upward extending transverse sidewallsof base 13. Combination members 105 act as clamping panels 89 of FIGS. 3and 4 to hold package 17 against the conductive panels 93 and inaddition function as a top cover for the enclosure. In the closedposition a pair of hooks 107 engage pins 109 on the members 105 to holdthe members tightly closed.

Although an exemplary embodiment of the invention has been shown anddescribed, many changes, modifications, and substitutions may be made byone having ordinary skill in the art without necessarily departing fromthe spirit and scope of this invention.

I claim:

1. Apparatus for rapidly heating food in a container completelyconductive adjacent the food between first and second generally opposededge portions comprising rigid enclosure means for substantiallyenclosing the conductive container, said enclosure means including abase and an openable cover for providing access to the interior of theenclosure means to allow insertion or removal of the conductivecontainer;

a step-down transformer having a primary electrically connectible tostandard line voltage for providing at a secondary a low voltagesubstantially less than 1 10 volts;

first and second clamping means mounted on and supported by theenclosure means for clampingly engaging the first and second edgeportions of the conductive container, respectively; I

mechanical advantage latching means forcing said container edge portionsand said clamping means into close low resistance engagement; and

means for electrically connecting each of said clamping means to thesecondary of said step-down transformer to supply current from saidtransformer through said container to rapidly heat the food.

2. The combination of claim 1 wherein the secondary of said transformerforms a portion of said clamping means and directly engages the edgeportions of the conductive container. v

3. The combination of claim 1 wherein said clamping means provide anarrow line contact with the edge portions of said container.

4. A combination as defined in claim 1 wherein said first clamping meansincludes a first elongated upstanding rigid member supported by saidbase for supporting the container along the first edge portion thereof,at least a portion of said member being electrically conductive andengaging the first edge portion of the conductive container along asubstantial length thereof, and means for retaining said first edgeportion on said first member.

5. A combination as defined in claim 1 including thermostat meansresponsive to the temperature of the conductive container rising to apredetermined value for automatically halting the flow of current fromsaid transformer to said first and second clamping means.

6. A combination as defined in claim 1 wherein said transformer forms atleast a portion of said base.

7. The combination of claim 1 wherein said container is supported inclosely spaced relationship to said transformer to minimize transformerleakage reactance losses and resistance losses in said secondary.

8. Apparatus for rapidly heating food in a container completelyconductive adjacent the food between first and second generally opposededge portions comprising a step-down transformer having a primaryelectrically connectible to standard line voltage for providing at asecondary a low voltage substantially less than 1 l0 volts;

first and second clamping means for clampingly engaging the first andsecond edge portions of the conductive container, respectively, whereinthe secondary of said transformer forms a portion of said clamping meansand directly engages the edge portions of the'conductive con- .tainer,

mechanical advantage latching means forcing said con 9. The combinationof claim 8 wherein said clamping means provide a narrow line contactvwith the edge portions of said container. I

10. A combination as defined in claim 8 including thermostat meansresponsive to the temperature of the conductive container rising to apredetermined value for automatically halting the flow of current fromsaid transformer to said first and second clamping means. i

11. The combination of claim 8 wherein said container is supported inclosely spaced relationship to said transformer to minimize transformerleakage reactance losses and resistance losses in said secondary.

* IR l

1. Apparatus for rapidly heating food in a container completelyconductive adjacent the food between first and second generally opposededge portions comprising rigid enclosure means for substantiallyenclosing the conductive container, said enclosure means including abase and an openable cover for providing access to the interior of theenclosure means to allow insertion or removal of the conductivecontainer; a step-down transformer having a primary electricallyconnectible to standard line voltage for providing at a secondary a lowvoltage substantially less than 110 volts; first and second clampingmeans mounted on and supported by the enclosure means for clampinglyengaging the first and second edge portions of the conductive container,respectively; mechanical advantage latching means forcing said containeredge portions and said clamping means into close low resistanceengagement; and means for electrically connecting each of said clampingmeans to the secondary of said step-down transformer to supply currentfrom said transformer through said container to rapidly heat the food.2. The combination of claim 1 wherein the secondary of said transformerforms a portion of said clamping means and directly engages the edgeportions of the conductive container.
 3. The combination of claim 1wherein said clamping means provide a narrow line contact with the edgeportions of said container.
 4. A combination as defined in claim 1wherein said first clamping means includes a first elongated upstandingrigid member supported by said base for supporting the container alongthe first edge portion thereof, at least a portion of said member beingelectrically conductive and engaging the first edge portion of theconductive container along a substantial length thereof, and means forretaining said first edge portion on said first member.
 5. A combinationas defined in claim 1 including thermostat means responsive to thetemperature of the conductive container rising to a predetermined valuefor automatically halting the flow of current from said transformer tosaid first and second clamping means.
 6. A combination as defined inclaim 1 wherein said transformer forms at least a portion of said base.7. The combination of claim 1 wherein said container is supported inclosely spaced relationship to said transformer to minimize transformerleakage reactance losses and resistance losses in said secondary. 8.Apparatus for rapidly heating food in a container completely conductiveadjacent the food between first and second generally opposed edgeportions comprising a step-down transformer having a primaryelectrically connectible to standard line voltage for providing at asecondary a low voltage substantially less than 110 volts; first andsecond clamping means for clampingly engaging the first and second edgeportions of the conductive container, respectively, wherein thesecondary of said transformer forms a portion of said clamping means anddirectly engages the edge portions of the conductive container,mechanical advantage latching means forcing said container edge portionsand said clamping means into close low resistance engagement; and meansfor electrically connecting each of said clamping means to the secondaryof said step-down transformer to supply current from said transformerthrough said container to rapidly heat the food.
 9. The combination ofclaim 8 wherein said clamping means provide a narrow line contact withthe edge portions of said container.
 10. A combination as defined inclaim 8 including thermostat means responsive to the temperature of theconductive container rising to a predetermined value for automaticallyhalting the flow of current from said transformer to said first andsecond clamping means.
 11. The combination of claim 8 wherein saidcontainer is supported in closely spaced relationship to saidtransformer to minimize transformer leakage reactance losses andresistance losses in said secondary.